/Engine/Source/Runtime/GeometryCore/Public/Selections/MeshConnectedComponents.h
Find all connected triangle components that contain one or more Seed Triangles and store in Components array. Search only starts from Seed Triangles. Triangle connectivity is based on edge connectivity, ie bowtie-vertices are not connections between triangles.
void FindTrianglesConnectedToSeeds ( const [TArray](API\Runtime\Core\Containers\TArray)< int > & SeedTriangles, [TFunction](API\Runtime\Core\GenericPlatform\TFunction)< bool(int32, int32)> TrisConnectedPredicate )